Error: -2146233079: Timeout expired. The timeout period elapsed prior to obtaining a connection from the pool. This may have occurred because all pooled connections were in use and max pool size was reached.

To use SQL Server, set this to
Server=server;Initial Catalog=database;MultipleActiveResultSets=true;Integrated Security=SSPI; for Integrated Authenticationor Server=server;Initial Catalog=database;MultipleActiveResultSets=true;User Id=sqlserveruser;Password=sqlserverpassword; for SQL Server Authentication

To use Access, set this to Provider=Microsoft.Jet.OLEDB.4.0;Data Source=filename